RDB
A database in which information is logically organised as a collection of related tables. Each table is a Relation made up of tuples (rows) and attributes (columns). Each attribute is some characteristic of the information. For example, if the Relation (table) contains information about people, the attributes (columns) might be first name, last name, address, etc. Each tuple (row) stores attribute values: the actual name, address, etc. for one specific person. This organizational structure allows great flexibility in creating views, subsets of the information, often extracted from different Relations (tables) in the database. Views can be easily queried and updated using a query language, typically SQL, to retrieve and manage the stored information.
More: Relational Database